This invention relates generally to devices for displaying information or images, and more particularly, to a display apparatus for producing an optical illusion of displayed images using time/position multiplexing and persistence of vision of a viewer.
The characteristic persistence of vision of human viewers has been used to advantage in previous display devices. The Bell U.S. Pat. No. 4,470,044 uses a modulated array of lights to create momentary perceptible visual images when scanned asynchronously by the human eye. There, the display device relies on saccadic eye movement between two points of eye fixation, the device itself remains stationary.
The Nobile et al. U.S. Pat. No. 5,057,827 describes a motor actuated rotating member where an array of LEDs are turned on and off using time or position division multiplexing so that to an observer an image is generated over the path of the array.
The McEwen et al. U.S. Pat. Nos. 5,180,912 and 5,192,864 describe a linear array of LEDs that also is stationary. There, a rotating mirrored surface or facet of a polygon is used to create the effect of rotary motion of the LED array. The persistence of vision of a human observer produces a two dimensional image as the LEDs are selectively controlled.
The Belcher et al. U.S. Pat. No. 5,302,965 describes a rotating display device which rotates vertical columns of light emitting diodes. The light emitting diodes arranged in the columns sweep around a cylindrical surface. A control circuit turns the light emitting diodes on and off to provide an image display on the surface. The Belcher et al. display device requires a complex electromechanical device with a motor for rotating the LED columns at a uniform rate of rotation.
The Eason U.S. Pat. No. 5,748,157 describes a hand held wand with an LED column actuated by an inertial switch. The wand can be swung back and forth while the lights are periodically turned on and off.
The Tokimoto U.S. Pat. No. 5,548,300 also describes a manually operated wand with an array of LED lights. The wand can be swung around an operating fulcrum. The fulcrum supplies relative angular position information and rotation speed information for synchronizing the turning of the lights.
A disadvantage of traditional persistence of vision display devices is that complex electromechanical devices are required for producing uniform oscillating or rotating. The prior art devices also cannot readily adjust to different and variable periods or cycle times in different uses. The devices with a singular linear array of light are also not suited for slowly moving display systems, or for use in conditions where there is a significant amount of ambient background light.
A light display is mounted on a bicycle wheel. The display includes a plurality of arrays of lights. The arrays include at least one master array, and a number of additional slave arrays. Each of the arrays is attached to a spoke of the bicycle wheel. A sensor mounted on the wheel is actuated by a magnet mounted on the bicycle frame. The sensor is used to determine the angular velocity of the wheel. The sensor can be attached to a coil of wire where a current is induced when the coil passes through the magnetic field.
A microprocessor, mounted on the wheel and connected to the sensor, and individually connected to each array of lights by a cable, includes a memory which stores a plurality of display patterns. The microprocessor modulates the plurality of arrays of light according to a selected one of the plurality of display patterns and the sensed angular velocity of the rotating wheel to form an image using persistence of vision of a viewer.
As an advantage, the display device with multiple light arrays can be used by rotating objects having a relatively low angular velocity, such as a bicycle wheel. In addition, with multiple reinforcing lights, the device can be used in places where there is a significant level of ambient background light, such as public roads.